Band-engineered GaTe/PdSe₂ van der Waals heterostructures for broadband polarization-sensitive photodetectors with reverse rectification

Anisotropic two-dimensional (2D) semiconductors have emerged as promising candidates for polarization-resolved photodetection due to their intrinsic in-plane optical anisotropies and linear dichroisms. However, their practical applications are often constrained by limited spectral response and low anisotropy ratios. In this work, we report a broadband polarization-sensitive photodetector based on a type-II p-GaTe/n-PdSe₂ van der Waals heterostructure, where interfacial band engineering—through the combined effect of the built-in p–n junction field and Schottky barrier—enables efficient carrier separation and unconventional reverse rectification. The device exhibits a high reverse rectification ratio (> 10²) and an ultra-low forward dark current (~ 10⁻¹¹ A). Owing to the engineered band alignment, it achieves broadband photodetection from 365 to 940 nm, with a high photo-switching ratio (> 10³), responsivity (~ 10³ A/W), detectivity (~ 10¹³ Jones), and external quantum efficiency (~ 10⁴%). Furthermore, strong polarization sensitivity is demonstrated, with polarization ratios of 5.39, 4.71, and 4.60 at the wavelengths of 365, 520, and 940 nm, respectively, highlighting the potential of this heterostructure for high-performance and polarization-resolved optoelectronic applications.